Designing green-emissive Cu,N-codoped carbon dots by pyrolysis of aromatic precursors and application in sensing of Fe( iii ) and Cr( vi )

formation of a non-fluorescent coordination complex with surface functional groups of the Cu,N-CDs, while Cr(vi) quenching arises primarily from the inner filter effect. The Cu,N-CDs offered high selectivity with low limits of detection for Fe(iii) (1.48 µM) and Cr(vi) (19.6 nM). The scalable, solvent-free synthetic strategy and the dual-analyte sensing capability demonstrated here position these Cu,N-CDs as promising platforms for practical deployment in environmental water monitoring, food safety screening for detection of heavy metal pollutants.